The present invention relates to gas turbines, especially to stationary industrial gas turbines, as are reproduced in FIG. 1 in a perspective, partially sectioned view. FIG. 1 shows a gas turbine 10 of the GT26 type of ALSTOM. Combustion air is inducted in this gas turbine 10 by a compressor 12 via an air intake 11, and compressed, and fed into a first combustion chamber 13 for combusting a fuel. Arranged downstream of the first combustion chamber 13 is a first (high-pressure) turbine 14 which is driven by the hot gases from the first combustion chamber 13. Provided downstream of the first turbine 14 is a second combustion chamber 15 in which a fuel is combusted together with the residual oxygen which is present in the hot gases. The hot exhaust gases from the second combustion chamber 15 drive a second (low-pressure) turbine 16 before they are discharged via a gas duct 17 to the outside or (in a combined cycle power plant) discharged into a subsequent heat recovery steam generator.
The gas duct 17 comprises a (basically cylindrical) inner casing 19 which usually serves for accommodating the exhaust gas-side rotor bearing and is enclosed concentrically and at a distance by an outer casing 18. Both casings 18 and 19 are interconnected by means of radial support struts 20 which are arranged in a distributed manner over the circumference. Through the gas duct 17, the hot exhaust gases are discharged from the gas turbine 10. For protection against the hot exhaust gases, the outer casing 18, the inner casing 19 and the support struts 20 are provided in each case with a lining or covering.
In the past, according to FIG. 2, different preformed parts were welded together to form in each case a top half 21a and a bottom half 21 b of the gas duct 17′. The two halves 21a and 21b were then fastened via brackets on the support structure of the exhaust-gas housing and after being joined together were welded in the parting plane by means of welded joints 22 in order to achieve a closed flow duct.
As a result of this type of construction and assembly, various problems or disadvantages arose, however:
1. A susceptibility to cracks in the gas duct, specifically created by                a. stress accumulation, namely                    i. large inherent stresses of the gas duct as a result of the welding, and            ii. high thermal stresses;                        b. severe vibrations in combination with low natural frequencies of the gas duct;        
2. poor scope for maintenance and repair.
Proposed in U.S. Pat. No. 4,920,742 for gas turbines is a support structure for supporting a segmented flow-path lining, which comprises a support bracket which is connected to a frame section and has a support device which is connected to the flow-path lining, wherein the support bracket is provided with a clearance hole in order to ensure a freely floating connection for free acceptance of axial and circumferentially occurring thermal expansion and contraction of the flow-path lining. The segmentation, however, is limited to the concentric regions of the flow-path lining and does not extend to the support struts and is comparatively coarse so that thermal stresses still constitute a problem and the scope for maintenance and repair is limited.